Effect of monomeric sequence on nanophase-segregated structure and water transport in Nafion 117

A study on the effect of monomer sequence on the structure and transport in hydrated Nafion 117 by Molecular Dynamics (MD) simulations was carried out to elucidate the effect of the monomeric sequence of polar (P) and nonpolar (N) monomeric units in Nafion on the phase-segregated morphology and water/hydronium transport. MD simulations were conducted at 300 and 353 K, relevant for fuel cell operation under isobaric-isothermal conditions. Nafion with 20 wt % water showed a segregated structure with water and polymer domains. Water domains were far from spherical, indicating that minimization of the interfacial area is not the determining factor as was assumed in simplified models. The monomer sequence of the polyelectrolyte had an effect on the extent of segregation: the more blocky sequence has better phase segregation. The vehicular transport of water and hydronium were not affected significantly by the monomeric sequence.